The invention concerns a device for a hydraulic adjustment of the angular position of a shaft relative to a drive pinion, said device comprising a plate fixed to the shaft to cooperate with the drive pinion for adjusting the angular position.
A device of the pre-cited type is known, for example, from U.S. Pat. No. 3,109,417. In this and other known devices, vanes of a vane rotor divide each cell of a cell rotor into two chambers sealed relative to each other, at least one of which chambers can be pressurized. When the engine is turned off, the pressure medium flows out of the chambers through supply or discharge ducts and leak gaps.
Another device for hydraulically adjusting the angular position of a shaft, particularly a camshaft of an internal combustion engine, relative to a drive pinion is known from DE 39 37 644 A1. This device comprises a vane rotor that is fixed to the shaft and comprises radial vanes, and a cell rotor arranged on the drive to receive the vanes in circumferentially spaced cells. This device enables a pressure-controlled, hydraulic angular adjustment of the vane rotor relative to the cell rotor out of an initial position when the operation of the engine begins. To avoid a relative movement between the vane rotor and the cell rotor in the starting phase when the supply of pressure medium to the device is insufficient, the device comprises a locking device for locking the vane rotor to the cell rotor. A drawback of this device is that it is relatively expensive due to the need of vane rotors. If these vane rotors that have a relatively complex shape are made, for example by sintering, precisely defined fabrication methods must be used, and a further drawback is that a very complex and therefore cost-intensive finishing is required.
EP 0 807 747 A1 likewise discloses a device for hydraulic angular adjustment in which a vane rotor that can rotate in a cell rotor is used. The vanes are fitted into corresponding grooves of the rotor on which they are arranged. This solution necessitates a large number of separate parts and, due to the fact that the vanes have to be fitted into the grooves, exact tolerances must be respected. Consequently, this solution is also relatively complex and expensive.
It is an object of the invention to provide a device for hydraulic angular adjustment, particularly of a camshaft relative to a crankshaft, which can be manufactured in a simpler and more economic manner than conventional devices.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The invention achieves the above objects by the fact that the device comprises:
at least one ring-segment shaped section arranged in the plate,
a dividing means arranged on the drive pinion for dividing the shaped section into two separate chambers sealed relative to each other, and
a means for a selective hydraulic pressurization of the chambers for adjusting the relative angular position of the drive pinion and the shaft.
The invention therefore provides a very simple-to-manufacture device for the hydraulic angular adjustment of a shaft relative to a drive pinion. In contrast to conventional solutions in which the vanes of a vane rotor are radially connected to the rotor, the invention permits a substantially axial connection of segments or components that take over the function of conventional vanes. Plates arranged on the drive pinion and on the driven element that correspond in function to known vane rotors and cell rotors can now be made in a substantially simpler manner. It is to be noted that the term, xe2x80x9cshaped sectionxe2x80x9d as used in the present context particularly includes impressions, cavities, elevations, grooves and slots.
In a first preferred embodiment of the device of the invention, the shaped section in the plate that is connected rotationally fast to the camshaft is configured as a pocket or cavity, and the dividing means that cooperates with the shaped section for forming the two separate chambers is configured on the drive pinion as a ring-segment shaped projection that engages the pocket, the angular extent of the projection being smaller than the angular extent of the ring-segment shaped section of the first plate. In this embodiment, both the plate that is connected rotationally fast to the camshaft as well as the drive pinion can be manufactured by very simple fabrication methods. In a simple manner, shaping techniques can be used in the case of metallic materials and injection molding methods in the case of plastics. By making the angular extent of the projection smaller than the angular extent of the shaped section, a range of adjustment within which an angular adjustment is to be effected can be defined in a simple manner.
In a further preferred embodiment of the device of the invention, the drive pinion comprises two spaced walls connected to each other preferably through end faces, the plate connected rotationally fast to the shaft is arranged between the two walls, the shaped section is configured as a slot, and the dividing means for forming the separate chambers is a component that engages the slot and is in contact with the two walls. This embodiment is likewise relatively simple to manufacture and is robust and reliable in practice.
Advantageously, the component is inserted into aligned bores of the two walls and secured against axial displacement. A particularly simple and economic measure is proposed for fixing the cylindrical component on the drive pinion in that, axial securing is effected, for example, by swaging. If the bores are circular in shape and the component inserted therein has a corresponding cylindrical configuration, said component can execute a rolling motion within the slot during a relative displacement between the shaft and the drive pinion. However, it is also conceivable to fix the component in the bores so that a sliding motion can take place.
In a further preferred embodiment of the invention, the component in contact with the two walls of the drive pinion is configured as a spacer sleeve through which the first wall of the drive pinion is force-locked to the second wall by a screw connection. In this embodiment, a component rigidly fixed to the walls of the drive pinion extends through the slot thus leading to the formation of a particularly simple and robust structure. To simplify the description, the first wall of the drive pinion will be referred to in the followings as the drive pinion, as such, and the second wall, as a cover.
Advantageously, the component engaging the slot is configured with a sealing means on its outer peripheral surface. With the help of such a sealing means, a leakage between the chambers that can occur due to component tolerances and the mounting conditions of the drive pinion on the shaft can be avoided in a simple manner. This measure proves to be particularly advantageous if the component (spacer sleeve) that extends through the slot is rigidly connected to the drive pinion.
Preferably, the sealing means is configured as a plastic sleeve made particularly of a glass fiber reinforced, high-temperature resistant plastic, that can be mounted on the component. Such a plastic sleeve can be mounted in a simple manner on the component preferably having a cylindrical shape, and guarantees an efficient sealing between the chambers.
Advantageously, the sealing means comprises a protruding lip and can be loaded by a pre-stressed torsion spring. This measure guarantees that even tolerances or unevenness on the slot walls can be compensated for by an appropriate twisting of the sealing means.
According to a further feature of the invention, the sealing means is made as a shaped part, particularly as a sleeve having sealing properties. With such shaped parts, too, a good sealing action can be obtained in a simple manner.
In a further preferred embodiment of the device of the invention, the device comprises a pin-type locking device that may be operated hydraulically or mechanically to enable a mechanical securing of the drive pinion on the plate that is fixed to the camshaft.